This is probably due to the code I gave you a while ago, if the total height exceeds the postbody height, it will overlap.You could try removing the overflow: visible; part of the codes I gave you, that might solve it.

The answer I had previously given to him in another thread (http://help.forumotion.com/t124235-signature-size-problem) was causing this, I noticed my mistake and corrected the code to exclude overflow: visible; in both parts.